Air actuator is stuck in defrost mode, I only have high air flow?

Hi,

The issue with fan speed is likely the result of a failed blower motor resistor. When they fail, high speed is the only speed that will work.

As far as the defroster-only air flow is concerned, there is likely a vacuum leak. The mode control knob operates a rotary vacuum switch that routes the engine vacuum to specific hoses in the vacuum harness. These hoses control vacuum actuators on the defroster duct. Each actuator operates an air valve (a door-like hinged deflector) that routes airflow to the various outlets of the heater/defrost system.

If you look at pic 1 below, I highlighted the blower motor resistor. Replace this part.

The remaining pics are the vacuum schematics for the HVAC system, both interior and under the hood. They are a little difficult to decipher, so let me know if you have questions.
Also, if you check those hoses with the engine running, you may hear a hissing sound from the leak. Also, check the supply under the hood to make sure the vacuum is making it inside the vehicle.

Let me know if this helps and what you find.

Take care,

Joe

See pics below.

Hi,

You are very welcome. When you do check the resistor, make sure the connector is in good condition and has not melted.

Take care and let me know what you find.

Joe

Hi,

The radio shut the truck off? As far as the switch is concerned, does it have an aftermarket security system? I ask because I've seen ones that require a switch to be toggled for it to start.

I'm not sure if you are looking for power distribution, but I attached them below. If you needed something different, let me know.

Take care,

Joe

See pics below: Note: I had to cut each pic in half to make them readable. I did overlap them so you can follow from one to the next.